1. Close any open Excel windows.
2. Click 'Start' and then click 'Run' from Windows XP; click the 'Microsoft' button and then click 'Run' from Vista; or click the 'Microsoft' button, then type 'Run,' then click 'Run' from Windows 7.
3. Type 'excel.exe /unregserver' into the text box and then click 'OK.'
4. Type 'excel.exe /regserver' into the textbox and then click 'OK.'